The Nervous System

1. NERVOUS SYSTEM
CYRUS KIMANTHI
December 2021

2. LECTURE OUTLINE
1. INTRODUCTION TO THE NERVOUS SYSTEM
2. OVERVIEW OF PARTS OF THE BRAIN AND CRANIAL MENINGES
3. FUNCTIONAL LOCALIZATION OF THE CEREBRAL CORTEX
4. BASAL GANGLIA, DIENCEPHALON AND THE CEREBELLUM
5. BRAINSTEM AND CRANIAL NERVES
6. SPINAL CORD ANATOMY
7. CSF & VENTRICULAR SYSTEM
8. DEVELOPMENT OF THE NERVOUS SYSTEM
2

3. SECTION I:
INTRODUCTION TO NERVOUS SYSTEM

4. SECTION I OBJECTIVES
1. State the role of the nervous system
2. Outline the divisions and subdivisions of the nervous system
3. Components of the nervous tissue
4. Types of neuroglial cells and the functions of each
5. Structure and classification of neurons
6. Differentiate between grey and white matter
4

5. DIVISIONS OF THE NERVOUS SYSTEM
Central nervous system Peripheral nervous system
6

6. PERIPHERAL NERVOUS SYSTEM
 Cranial nerves (12 Pairs)
 Spinal nerves (31 Pairs)
 Afferent [sensory] division
 Efferent [motor] division
7
ANATOMICAL DIVISION FUNCTIONAL DIVISION
Based on the CNS origin Based on impulse direction
of the peripheral nerves (with respect to the CNS)

7. EFFERENT DIVISION OF THE NERVOUS SYSTEM
 Somatic nervous system
 Targets skeletal muscles
 Autonomic nervous system
 Targets smooth muscles,
cardiac muscles and glands
Nerve supply to effector organs (muscles & glands)
Based on how the CNS controls the effectors
Under voluntary control Under involuntary control

8. AUTONOMIC NERVOUS SYSTEM
 Targets cardiac muscles,
smooth muscles, glands
Divisions:
1. Sympathetic division
2. Parasympathetic division
3. Enteric nervous system*
9

9. CLASS DISCUSSION
Outline the differences between the
autonomic and somatic nervous systems

11. DIFFERENCES BETWEEN SOMATIC AND AUTONOMIC DIVISIONS
OF THE NERVOUS SYSTEM
PARAMETER SOMATIC DIVISION AUTONOMIC DIVISION
Number of peripheral
processes
One Two
Horn of origin from t
he spinal cord Ventral horn Lateral horn
Spinal cord
segments of origin All segments
T1-L2 for sympathetic
S2-S4 for parasympathetic
Nerve fiber type All are myelinated Postganglionic are
unmyelinated
Target organs
(effectors) Skeletal muscles
Cardiac muscle, glands
smooth muscles

12. DIFFERENCES BETWEEN SOMATIC AND AUTONOMIC NERVOUS
SYSTEMS
PARAMETER SOMATIC DIVISION AUTONOMIC DIVISION
Type of CNS control Voluntary Involuntary
Presence of ganglia None Present
Neurotransmitter All are cholinergic
Cholinergic, adrenergic
and others
Type of cholinergic
receptors
Muscle type nicotinic
receptors
Muscarinic & Neurona
nicotinic receptors
Endocrine
component
None
Adrenal gland
[sympathetic division]

13. CELLS OF THE NERVOUS TISSUE
14
NEURONS NEUROGLIAL CELLS
Functional cells Supporting cells
Excitable cells Non-excitable cells
Largely non-renewing Renewing cells
Fewer Outnumber neurons

14. TYPES OF NEUROGLIAL CELLS
a) Central neuroglia
 Astrocytes
 Oligodendrocytes
 Ependymal cells
 Microglia
15

15. TYPES OF NEUROGLIAL CELLS
16
b) Peripheral neuroglia
Schwann cells Satellite cells

16. NEURON (NERVE CELLS)
1. Excitability:
 Ability to generate a bioelectric
impulse (action potential)
2. Conductivity:
 Ability to transmit an action
potential along some distance
17

17. STRUCTURE OF NEURONS
Neurons have three functional domains:
1. Receptive domain
3. Transmission domain
2. Integration domain
18

18. CLASSIFICATION OF NEURONS
Based on number of processes arising from the cell body
Multipolar neuron
Bipolar neuron
Pseudounipolar neuron
19
STRUCTURAL CLASSIFICATION

19. CLASSIFICATION OF NEURONS
Afferent = Sensory neuron
Efferent = Motor neuron
Association = Interneuron
20
FUNCTIONAL CLASSIFICATION
Based on the direction of nerve impulses

20. GREY AND WHITE MATTER
Grey matter:
 Collection of cell bodies
 Cortex (cortices)
 Nucleus (nuclei)
 Ganglion (ganglia)
21

21. GREY AND WHITE MATTER
White matter:
 Axonal fibers
 Projection fibers
 Association fibers
 Commissural fibers
22

22. SECTION II:
OVERVIEW OF PARTS OF THE
BRAIN AND CRANIAL MENINGES

23. SECTION II OBJECTIVES:
1. Review of parts and contents of the cranial cavity
2. Review of meningeal layers and meningeal spaces
3. Parts of the brain and subparts of the brain
4. Lobes of the cerebral cortex
5. Microscopic structure of the cerebral cortex
24

24. Anterior cranial fossa:
Frontal lobe
Olfactory pathway
PARTS AND CONTENTS OF THE CRANIAL 25
CAVITY

25. Middle cranial fossa:
Temporal lobes
Pituitary gland
Internal carotid arteries
CN II - VI
PARTS AND CONTENTS OF THE CRANIAL 26
CAVITY

26. Posterior cranial fossa:
Hindbrain
Vertebrobasilar system
CN VII - XII
PARTS AND CONTENTS OF THE CRANIAL 27
CAVITY

27. MENINGEAL LAYERS AND SPACES
 Meningeal layers:
 Dura matter
 Arachnoid matter
 Pia matter
28

28. MENINGEAL LAYERS AND SPACES
Meningeal spaces:
 Epidural (extradural)
 Subdural space
 Subarachnoid space
 Dural venous sinuses*
29

29. BASIC PARTS OF THE BRAIN
30
Cerebrum
Cerebellum
Brainstem:
Midbrain
Pons
Medulla oblongata

30. PARTS OF THE BRAIN II
 Forebrain (procencephalon)
 Midbrain (mesencephalon)
 Hindbrain (rhombencephalon)
31

31. PARTS OF THE CEREBRUM
Cerebral hemispheres
(Telencephalon)
Diencephalon
32

32. PARTS OF THE CEREBRAL HEMISPHERE
Cerebral cortex
Cerebral white matter
Basal nuclei
33

33. PARTS OF THE CEREBRAL CORTEX
 Gyri (gyrus) – Ridges
 Sulci (sulcus) – Furrows
 Lobes: Frontal, Parietal,
Occipital & Temporal
34

34. 35

35. MICROSCOPIC STRUCTURE OF THE
CEREBRAL CORTEX
36

36. SECTION III:
FUNCTIONAL LOCALIZATION OF THE
CEREBRAL CORTEX

37. SECTION III OBJECTIVES
1. Identify the major each lobe of the cerebral cortex
2. Name the major functional areas in each lobe of the cerebral
cortex, and state the role of each
3. Work out possible clinical presentations due to lesions in various
cortical areas
4. Describe the blood supply to the cerebral cortex
38

38. For each lobe:
1. Gyrus
2. Functional area – name
3. Brodmann's number*
4. Function/role
5. Effects of injury (stroke,
tumor, trauma)
FUNCTIONAL LOCALIZATION OF THE 39
CEREBRAL CORTEX

39. SUMMARY OF BRODMANN’S AREAS
40

40. FUNCTIONAL LOCALIZATION OF THE
CEREBRAL CORTEX – FRONTAL LOBE
41

41. 42
BRODMANN’S
FUNCTION
CLINICAL
RELEVANCE
Precentral Primary
Motor
4 Voluntary
movements
Inferior
frontal
Broca’s 45;44 Motor
speech
Frontal
pole
Prefrontal
9;
10;
11
Higher
“cognitive”
Contralateral
hemiplegia
Expressive
aphasia
Impaired
cognition

42. FUNCTIONAL LOCALIZATION OF THE
CEREBRAL CORTEX – FRONTAL LOBE
44

43. 45
BRODMANN’S
FUNCTION
CLINICAL
RELEVANCE
Frontal eye
field
8 Conjugate
gaze
Diplopia
Middle
frontal
Superior
frontal
Premotor 6 Voluntary
movements
Contralateral
hemiplegia
Medial
frontal
Supplementary
motor
24 Voluntary
movements
Contralateral
hemiplegia

44. FUNCTIONAL LOCALIZATION OF THE
CEREBRAL CORTEX – PARIETAL LOBE
46

45. 47
BRODMANN’S
FUNCTION
CLINICAL
RELEVANCE
Postcentral
Primary
somatosensory
3;
1;
2
Contralateral
anaesthesia
Superior
parietal lobule
Secondary
somatosensory 5;7
Perception of
general
sensations
Recognition of
general
sensations
Agnosia
Supramarginal
& Angular
Wernicke’s
39;
40
Sensory speech
Receptive
aphasia
Para-insular
region
Primary gustatory 43 Perception of
taste
Loss of taste
sensation

46. FUNCTIONAL LOCALIZATION OF THE
CEREBRAL CORTEX – OCCIPITAL LOBE
48

47. 49
BRODMANN’S
FUNCTION
CLINICAL
RELEVANCE
Banks of
calcarine
sulcus
Primary visual
cortex 17
Perception of
light input
Anopia
Cuneal
Lingual
Visual
association
cortices
18;
19
Recognition
of light input
Visual agnosia

48. FUNCTIONAL LOCALIZATION OF THE
CEREBRAL CORTEX – TEMPORAL LOBE
50

49. 51
BRODMANN’S
FUNCTION
CLINICAL
RELEVANCE
Primary
auditory
41;
42
Perception of
sound
Sensory-neural
hearing loss
Transverse
gyri of
Heschl
Superior
temporal
Secondary
auditory
22 Recognition
of sound
Auditory
agnosia
Piriform
Primary
olfactory
28;
34
Perception
of smell
Anosmia

50. THE LIMBIC SYSTEM
 Borders the cerebral hilum
In the temporal lobe:
 Hippocampus
 Parahippocampus
52

51. THE LIMBIC SYSTEM
Other parts:
 Cingulate gyrus
 Fornix
 Hypothalamus
 Anterior thalamus
53

52. FUNCTIONS OF THE LIMBIC SYSTEM
1. Emotions
2. Behavior
3. Short term memory
4. Sexual responses
5. Regulate food intake
54

53. BLOOD SUPPLY TO THE CEREBRAL CORTEX
55

54. THE THREE CEREBRAL ARTERIES
56

55. SECTION IV:
BASAL GANGLIA, DIENCEPHALON
AND THE CEREBELLUM

56. SECTION IV OBJECTIVES
1. Define “basal ganglia” and state its basic components
2. State the functions and disorders of the basal ganglia
3. Name the components of the diencephalon
4. State the functions of the thalamus, hypothalamus and the
pineal body
5. Parts, functions and disorders of the cerebellum
58

57. THE “BASAL GANGLIA”
 A group of nuclei at the base of
the cerebral hemispheres
 Correct term = Basal nuclei
 Involved in regulation of motor
functions
 Provide the “braking” system
during movements
59

58. COMPONENTS OF THE BASAL GANGLIA
1. Caudate nucleus
2. Putamen
3. Globus pallidum
o Subthalamus
o Substantia nigra
60

59. BASAL GANGLIA DISORDERS
Parkinson’s disease Chorea
61

60. THE DIENCEPHALON
1. Thalamus
1. Sensory relay center
2. Limbic functions
3. Motor functions (basal ganglia)
4. Cortical activation (alertness)
5. Cognitive functions
62

61. THE DIENCEPHALON
2. Hypothalamus
1. Control of autonomic functions
2. Endocrine functions
3. Limbic functions
4. Control of food intake
5. Various sensors*
63

62. THE DIENCEPHALON
3. Pineal gland (Epithalamus)
 Neuroendocrine transducer
 Secretes melatonin hormone
1. Anti-gonadic effects
2. Diurnal circadian rhythm - sleep
wake cycle
64

63. THE CEREBELLUM
 Located in the posterior cranial
fossa
 Separated from pons and
medulla by the 4th ventricle
65

64. THE CEREBELLUM
 Attached to brainstem via the
peduncles
 Parts include: Hemispheres;
Flocculus; Nodule; Tonsils and
Vermis
 Deep nuclei include: Dentate,
Emboliform, Globbose and Fastigial
66

65. 67
FUNCTIONS
Floculonodular Vestibulocerebellum Archicerebellum
Vermis
Tonsils
Spinocerebellum Paleocerebellum
Muscle tone
Truncal posture
Hemispheres Cerebrocerebellum Neocerebellum
Motor planning
Motor learning
Equilibrium
Eye movements

66. CEREBELLAR DISORDERS
 Nystagmus
 Ataxia
 Dysmetria
 Dysdiadochokinesia
 Hypotonia
 Intention tremors
 Dysarthria
68

67. SECTION V:
BRAINSTEM AND CRANIAL
NERVES

68. SECTION V OBJECTIVES
1. Name the components of the brainstem
2. State the main functions of the brainstem (or its parts)
3. Name the cranial nerves (in order)
4. State the distribution and function of each of the cranial nerves
5. State common deficits associated with injuries to cranial nerves
70

69. PARTS OF THE BRAINSTEM
71

70. FUNCTIONS OF THE BRAINSTEM
1. Connection: Spinal cord to brain; Cerebellum to cerebrum
2. Cortical activation: Maintain alertness
3. Vital centers: Cardiac, Respiratory and Vasomotor centers
4. Reflexes: Visual, Pupillary light, Auditory, Jaw-jerk, Corneal
5. Motor functions: Rubrospinal, Tectospinal, Vestibulospinal
6. Cranial nerve origin
72

71. THE CRANIAL NERVES
 Paired nerves
 Originate from the
brain(stem)*
 Numbered I – XII
 Exit cranial cavity
via skull foramina
73

72. MAJOR SKULL FORAMINA
AND THEIR CONTENTS
 Foramen magnum
 Carotid canal
 Optic canal
 Superior orbital fissure
 Foramen ovale
 Internal auditory meatus
 Jugular foramen
 Hypoglossal canal
74

73. 75
NUMBER & NAME DISTRIBUTION FUNCTION
I - Olfactory
Roof of nasal
cavity
Smell sensation
CLINICAL
Anosmia
II - Optic Retina Vision Anopia
III - Oculomotor
Extraocular M
Iris
Eye movements
Pupillary constriction
Strabismus
Mydriasis
IV - Trochlear Superior oblique Eye movements Strabismus

74. 76
NUMBER & NAME DISTRIBUTION FUNCTION CLINICAL
V - Trigeminal
V1 - Ophthalmic
V2 - Maxillary
V3 - Mandibular
Face & scalp General sensations
1st Arch muscles Mastication
VI - Abducens Lateral rectus Eye movements Strabismus
VII - Facial
2nd Arch muscles Facial expression Bell’s palsy
Tongue Taste sensation Loss of taste
Salivary glands
Lacrimal gland
Salivation
Lacrimation
Crocodile
tears

75. NUMBER & NAME DISTRIBUTION FUNCTION
VIII -
Vestibulocochlear
CLINICAL
77
Vertigo
IX -
Glossopharyngeal
SNHL
Loss of taste
X - Vagus
Vestibular
apparatus
Cochlear duct
Tongue
3rd Arch muscle
Parotid gland
6th Arch muscle
Epiglottis
Visceral organs
Equilibrium sensation
Hearing sensation
Taste
Swallowing
Salivation
Phonation
Taste
Parasympathetic
Dysarthria
Loos of taste
???

76. 78
NUMBER & NAME DISTRIBUTION FUNCTION
XI - Accessory 4th Arch muscles Swallowing
CLINICAL
XII - Hypoglossal Tongue muscles Tongue movements
Tongue
deviation
Slurred
speech

77. CLASS DISCUSSION
1. Name the cranial nerves that are purely sensory
2. Name all the cranial nerves with parasympathetic function &
state what each is parasympathetic to [10 marks]
3. Name the nerves that innervate the eyeball and state the
role of each [20 marks]
4. Outline the innervation of the tongue [15 marks]
79

78. SECTION VI:
SPINAL CORD ANATOMY

79. SECTION VI OBJECTIVES
1. State the extends and enlargements of the spinal cord
2. Outline the origin and organization of a spinal nerve
3. Describe the internal structure of the spinal cord
4. Name the major tracts of the spinal cord and state the modality
of each
81

80. SPINAL CORD ANATOMY
 Extends from the medulla oblongata
 Ends as the conus medullaris, at:
1. L1/2 junction in adults
2. L3 at birth
3. S1 at 6 months foetal life
4. Cx at 3 months foetal life
82

81. SPINAL CORD ANATOMY
 Gives rise to pairs of spinal nerves
 C = 8; T = 12; L = 5; S = 5; Cx = 1
Spinal cord enlargements:
 Cervical = brachial plexus
Lumbar = Lumbosacral plexus
The cauda equina
83

82. SPINAL CORD CROSS-SECTIONAL ANATOMY
 Anterior median sulcus
 Posterolateral sulcus
 Central canal
 Grey matter
 White matter
84

83. SPINAL CORD CROSS-SECTIONAL ANATOMY
Spinal cord grey matter:
Anterior horn
Posterior horn
Lateral horn
85

84. SPINAL CORD CROSS-SECTIONAL ANATOMY
Spinal cord white matter
Contain axonal fibers
Classified as ascending
and descending tracts
86

85. SPINAL CORD CROSS-SECTIONAL ANATOMY
Main ascending tracts:
 Dorsal column tracts
 Spinothalamic tracts
 Spinocerebellar tracts
87

86. SPINAL CORD CROSS-SECTIONAL ANATOMY
Main descending tracts:
Pyramidal tracts:
Corticospinal tracts
Extrapyramidal tracts:
 Rubrospinal; Tectospinal;
Vestibulospinal
88

87. ARTERIAL BLOOD SUPPLY TO THE
SPINAL CORD
89

88. SPINAL MENINGES
Three layers of meninges
Filum terminale
Lumbar cistern
90

89. SECTION VII:
CSF & VENTRICULAR SYSTEM

90. SECTION VII OBJECTIVES
1. State the sources of the cerebrospinal fluid
2. Describe the flow of the cerebrospinal fluid
3. State how CSF is absorbed
4. Highlight on clinical relevance of CSF
92

91. CSF & VENTRICULAR SYSTEM
CSF is secreted by:
1. Choroid plexus
2. Ependymal lining of the ventricles
 The fluid flows through various CSF
spaces
93
SECRETION OF THE CEREBROSPINAL FLUID

92. CSF & VENTRICULAR SYSTEM 94
FLOW OF THE CEREBROSPINAL FLUID
LATERAL VENTRICLES [Cerebral hemispheres]
THIRD VENTRICLE [Diencephalon]
Interventricular foramen (of Monro)
FOURTH VENTRICLE [Hindbrain]
Cerebral aqueduct (within midbrain)
Central canal (of the spinal cord)

93. CSF & VENTRICULAR SYSTEM 95
FLOW OF THE CEREBROSPINAL FLUID
LATERAL VENTRICLES [Cerebral hemispheres]
THIRD VENTRICLE [Diencephalon]
Interventricular foramen (of Monro)
FOURTH VENTRICLE [Hindbrain]
Cerebral aqueduct (within midbrain)
Central canal (of the spinal cord)

94. CSF & VENTRICULAR SYSTEM 96
FLOW OF THE CEREBROSPINAL FLUID
FOURTH VENTRICLE
SUBARACHNOID SPACES
Median foramen
(of Magendie)
Lateral foramina
(of Luschka)
DURAL VENOUS CIRCULATION
CSF Absorption By Arachnoid villi

95. CSF & VENTRICULAR SYSTEM 97
FLOW OF THE CEREBROSPINAL FLUID
FOURTH VENTRICLE
SUBARACHNOID SPACES
Median foramen
(of Magendie)
Lateral foramina
(of Luschka)
DURAL VENOUS CIRCULATION
CSF Absorption By Arachnoid villi

96. CSF & VENTRICULAR SYSTEM 98
CLINICAL RELEVANCE OF THE CSF
Hydrocephaly Lumbar puncture

97. THANK YOU FOR YOUR
ATTENTION
121
THE END